Electronic musical system with magnetic field responsive switch and volume control

ABSTRACT

An electronic musical system has a tone generator and a tone coloring circuit with a first resistance connected in series between them. A second resistance has one end connected to the series circuit between the tone coloring circuit and the tone generator and the other end connected to ground. One of the resistances is a magnetoresistor, the electrical resistance of which varies in accordance with the intensity of the magnetic field applied thereto. A key is movably mounted above the magnetoresistor with a magnet element mounted thereon close to the magnetoresistor, so that movement of the key controls the electrical resistance of the magnetoresistor depending on the amount the key is moved.

United States Patent [72.] Inventor Junji Ohno Hamamatsu-shi, Japan [21]Appl. No. 806,574 [22] Filed Mar. 12, 1969 [45] Patented July 20, 1971[731 Assignee Nippon Gakki Seizo Kabushiki Kaisha Hamamatsu-shi, Japan[32] Priority Mar. 18, 1968, Mar. 22, 1968 [33] Japan [3 1 1 43/21336and 43/22491 [54] ELECTRONIC MUSICAL SYSTEM WITH MAGNETIC FIELDRESPONSIVE SWITCH AND VOLUME CONTROL 7 Claims, 8 Drawing Figs.

[52] US. Cl. 84/1.27, 84/1 .1 [51] Int. Cl G0lh 1/02 [50] Field ofSearch 84/1.01, 1.09, 1.1, 1.14, 1.15, 1.27, 1.13, 1.26; 307/259, 309;323/94 H; 317/235-23 [56] References Cited UNITED STATES PATENTS2,878,708 3/1959 Hanen 84/1.08

lnl 3,594,488

Primary Exaniiner Milton 0. I Hirshfield Assistant Examiner-Stanely JWitkowski Atmrney Wenderoth, Lind & Ponack ABSTRACT: An electronicmusical system has a tone generator and a tone coloring circuit with afirst resistance connected in series between them. A second resistancehas one end connected to the series circuit between the tone coloringcircuit and the tone generator and the other end connected to ground.One of the resistances is a magnetoresistor, the electrical resistanceof which varies in accordance with the intensity of the magnetic fieldapplied thereto. A key is movably v mounted above the magnetoresistorwith a magnet element mounted thereon close to the magnetoresistor, sothat movement of the key controls the electrical resistance of themagnetoresistor depending on the amount the key is moved.

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JUNJO ouNo BY MM Ar PATENTEDJULZOISTI 3,594 488 sum 2 OF INVENTOR.\JUNJI 01 m0 [Mm M3 ELECTRONIC MUSICAL SYSTEM WITH MAGNETIC FIELDRESPONSIVE SWITCH AND VOLUME CONTROL BACKGROUND OF THE INVENTIONHeretofor, electronic musical instruments have ordinarily been providedwith tone generators and switches which control the outputs of said tonegenerators. Accordingly, many electric contacts are always necessary forelectronic musical instruments, and for the electric contacts,metal-to-metal contacts or metal-tomonductive-rubber contacts have beenused conventionally. But, these are liable to cause bad contacts owingto .the formation of sulfides or oxides of metals or deposits of dust onthe surfaces of the contacts, and therefore they are unreliable, andfurthermore they causes a click signal in the moment of closing oropening of the switches. Moreover, said contacts can only switchelectric signals, and it is impossible to vary the volumes of soundssimply by varying the strength with which the keys are depressed.

SUMMARY OF THE INVENTION A principal object of the present invention isto provide a switch device for an electronic musical instrument withsocalled touch-sensitive control, wherein magnetic field applied to amagnetoresistor is varied by the strength with which the key isdepressed so as to control the sound volume.

The magnetoresistor of the present invention is an element the electricresistance of which increases as the intensity of the applied magneticfield increases or varies as the variation of intensity and direction ofthe applied magnetic field.

Other objects and advantages of the invention will appear more fullyhereinafter from a consideration of the detailed description whichfollows, taken together with the accompanying drawings wherein severalembodiments of the invention are illustrated. It is to be expresslyunderstood, however, that the drawings are for the purpose ofillustration and description only and are not designed as a definitionof the limits of the invention, reference being had for this purpose tothe appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a circuit diagram of a firstembodiment of a switch device according to the invention;

FIG. 2 is a vertical cross section of a keyboard fitted with saidcircuit;

FIG. 3 is a schematic perspective view of the main part of said switchdevice;

FIG. 4 is a circuit diagram illustrating a second embodiment of a switchdevice according to the invention;

FIG. 5 is a schematic perspective view of the main part of the switchdevice of the second embodiment;

FIG. 6 is a vertical cross-sectional view of a keyboard fitted with aplurality switch devices.

FIG. 7 is a circuit diagram illustrating a third embodiment of a switchdevice according to the invention; and

FIG. 8 is a vertical cross-sectional view of a keyboard fitted with saidcircuit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the figures, the numeral 1designates a tone generator the details of which are omitted.Magnetoresistors are shown at 2,

2', 2a and 2b, respectively, 4 designates a tone coloring circuit thedetails of which are omitted and 5 and 5' are magnets.

In FIG. I, a magnetoresistor 2 is connected in series between a tonegenerator I and atone coloring circuit 4, and a fixed resistor 3 isconnected between the output side of the magnetoresistor 2 and ground,and a potential divider is formed by said magnetoresistor 2 and thefixed resistor 3. Said magnetoresistor 2 is an element the electricresistance of which increases as the intensity of an applied magneticfield increases, and the intensity of the magnetic field of the magnet 5applied to the magnetoresistor 2 becomes a maximum when the key is in anoff-state and the intensity of the magnetic field of the magnet 5applied to the magnetoresistor 2 becomes less or zero whcnthc key'isinan on-statc. In said device, no output signal from the tone generatorI will appear at the output side of the magnetoresistor 2 when the keyis in the off-state, as the electric resistance of the magnetoresistor 2is a maximum, and the output signal of the tone generator I will besupplied to the tone coloring circuit 4 when the key is in the on-state,as the electric resistance of the magnetoresistor 2 is reduced. In thiscase, as the intensity of the magnetic field of the magnet 5 applied tothe magnetoresistor 2 decreases gradually the resistance of themagnetoresistor 2 decreases gradually. Thereby, touch sensitive controlis possible by the manipulation of a key; that is, when a key isdepressed to a small extent the signal supplied to the tone coloringcircuit 4 is weak, and when the key is depressed to a large extend thesignal supplied to the tone coloring circuit 4 becomes stronger.

FIGS. 2 and 3 illustrate the magnet 5 and the magnetoresistor 2, whereinthe magnet S is horseshoe shaped and fixed with a screw 8 to a key 6with a nonmagnetic spacer 7 between the magnet and the key, and themagnetoresistor 2 is fixed to a holding piece 10 which is fitted to akeyboard frame 9. Consequently, the magnetoresistor 2 is fixed and themagnet 5 moves with the key 6. And the magnet 5 and the magnetosensitiveelement 2 are setas near as possible, for instance, as shown in FIG. 3,such that the magnetoresistor 2 is held between the north pole and thesouth pole of the magnet 5,

. and moreover, they are set such that the intensity of the magneticfield applied by the magnet 5 to the magnetoresistor 2 becomes a maximumwhen the key is in the off-state and becomes less or zero when the keyis in the on-state.

FIG. 4' shows another circuit diagram of a second embodiment of theinvention, wherein the positions of the magnetoresistor 2 and the fixedresistance 3 as shown in FIG. I are interchanged. When themagnetoresistor 2 is similar to that of FIG. 1, wherein the intensity ofthe magnetic field applied by the magnet 5 to the magnetoresistor 2becomes a minimum when the key is in the off-state, and the intensity ofthe magnetic field applied by the magnet 5 to the magnetoresistor 2becomes larger when thc'key is in the on-state, then the same result asin the case of FIG. I is attained. I

Furthermore, when the element is a magnetosensitive diode in which theelectric current which flows varies according to the intensity ofapplied magnetic field, almost the same results are obtained as in thecase of a magnetosensitive resistor. FIG. 5 illustrates an example of aswitch device having a large control ratio utilizing the characteristicsof the magnetosensitive diode. That is, a magnetosensitive diode 2' isused, said diode 2' being positioned so as to move between pairs ofpoles of a multipolar magnet 5' which has pairs of poles in reversedpositions as shown in FIG. 5, wherein, the key is in the on-state themagnetic field is in a direction to permit an electric current to flowthrough magnetosensitive. diode 2, and when the key is in the off-statethe magnetic field is in the opposite direction so that an electriccurrent does not flow through magnetosensitive diode 2'. With thisarrangement, there is no fear of signal leakage in the off-state of thekey.

FIG. 6 illustrates an example of a key construction comprising amultiple switch device having a plurality of magnetoresistors and amultipolar magnet. The plurality of magnetoresistors 2', 2', are fixedto a holding piece 10 at suitable distances from each other and saidholding piece 10 is fixed to the keyboard frame 9. The multipolar magnet5 is fixed to a spring holder 12 by spring plates II so as to be drivendirectly or indirectly through a drivingpiece by the action of the key6, and said spring holder 12 is fixed to the keyboard frame 9. Themagnet 5' and each magnetoresistors 2' are to be positioned as near aspossible to each other and such that the intensity of the magnetic fieldcaused by the multipolar magnet 5' is applied to each magnetoresistors2' becomes a maximum when the key is in the off-state and becomes lessor zero when'the key is in the oil-state. Furthermore, if each elementis a maganother magnetoresistor 2b is connected between the output sideof the magnetoresistor 2a and ground a potential divider being formed bysaidtwo magnetoresistor-s21: and 2b. Said elements are magnetoresistorsthe electric resistances of which increaseas the magnetic fieldintensity increases. The

. intensity of magnetic field of the magnet to the magnetoresistor 2abecomes a maximum and the intensity of the magn'etic field of the magnet5 to the magnetoresistor 2b becomes a minimum when the key is in theoff-state, and on the contrary, the intensity of magnetic field of themagnet 5 applied to the magnetoresistor 2a becomes a minimum and theintensity of magnetic field of the magnet 5 applied to themagnetoresistorZb becomes a maximum when the key is in the on-state.

Accordingly, when the key is in the on-state, a large output signal fromthe tone generator 1 is transmitted to the tone coloring circuit 4,because the electric resistance of the magnetoresistor Za'becomesminimumand the electric resistance of the magnetoresistor 2b becomesmaximum.

Next, when the key is in the off-state, only a small part of the signalfrom the tone generator 1 is transmitted to the tone coloring circuit 4because the electric resistance of the magnetoresistor'2a becomes amaximum and the electric resistance of the magnetoresistor 2b becomes aminumum. Generally, a magnetoresistor has some value of resistance evenwhen amagnetic field is not applied thereto, and furthermore, it isimpossible to diminish the intensity of the magnetic .fieldappliedto'theinagnetoresistor 2b to zero owing to the structural limitation ofthe distance between the magnetoresister 2a and the magnetosensitiveelement 2b. According to the present embodiment, however, even in suchcase, the electric voltage across the terminals of the magnetoresistor2b becomes small and the output signal from the tone generator 1diminishes almost to zero, because the electric resistance of themagnetoresistor 20 becomes high.

Due to the action of the key in the on or off position, the values ofthe resistances of thev magnetoresistors 2a and 2b vary oppositely toeach other so the control ratio of the output signals becomes extremelylarge. \ln the above description, although the cases .wherein the key isin the extreme on or off position has been described, the portion of theoutput signal from the tone generator 1 applied to the tone coloringcircuit 4 may be varied corresponding to the extent of depression'of thekey, because the values of the resistances of the magnetoresistors 2aand 2b vary gradually corresponding to the extent of the depression ofthe key.

Therefore, so-called touch-sensitive control effect is attained.

FIG.- 8 illustrates an arrangement of said magnet and saidmagnetoresistor, wherein the magnet 5 is fixed to the key 6 through anonmagnetic spacer 7, and magnetoresistors 2a and 2b are fixed to anelectric insulating holder plate 10' mounted on the keyboard frame9.Consequently, the magnetoresistor 2a and lb are immovable and the magnet5 moves with. the key 6. In this case, the magnet 5 and themagnetoresistors 2a and 5 2b are positioned as near as possible to eachother, and the intensity of magnetic field of themagnet 5 applied to themagnetoresistor 2a, becomes a maximum and the intensity of the magneticfield of the magnet 5 applied to the magnetoresistor 2b becomes aminumum when the key is in the off-state. On

the contrary, the intensity of magnetic field of the magnet 5 applied tothe magnetoresistor 2a becomes minumum aNd the intensity of the magneticfield of the magnet 5 applied to the the on-state. t I

Furthermore, in the circuit of the third embodiment as shown in FIG. 7,it is clear that the same effect is obtainable when the tone generator 1and the tone coloring circuit 4 are substituted for each other so as tosupply the output signal of the tone generator I to the magnetoresistor2b and through magnetoresistor 2a to the tone coloring circuit 4.

In the above embodiments, it will beunderstood that a plurality ofmagnets may be used in place of the multipolar magnet, or electromagnetsmay be used instead of the permanent magnets. Y

Although, in the above all embodiments, the magnet is fixed to the keyand the magnetoresistor to the stationary part, it is clear that thesame effect can be obtained even when the magnetoresistor is fixed tothe key and the magnet to the stationary part.

As above described, the switch device of this invention is veryeffective from a practical standpoint, overcoming completely the defectsin switching the signal such as miscontacts and click signals withoutusing any contacts, and increasing the reliability and making the deviceitself small. Moreover, it makes possible touch-sensitive control with alarge control ratio.

The foregoing description contains a limited number of embodiments ofthe present invention. It will be understood, however, that suchembodiments are only illustrative and that numerous variations arepossiblewithout departing from the purview of the invention as-definedin the following claims.

I claim: v

1. An electronic musical system comprising a tone generator, a tonecoloring circuit, a first resistance means connected in a series circuitbetween said tone generator and said tone coloring circuit,.a secondresistance means having one end connected to the series circuit betweensaid first resistance means and said tone coloring circuit and the otherend connected to ground, at least one of said resistance means being amagnetoresistor the electrical resistance of which varies in accordancewith the intensity of the magnetic field applied thereto, a key meansmovably supported in said system so as to be depressed when it is moved,and a magnet element mounted on said key means close to saidmagnetoresistor and controlling the electrical resistance ofsaidmagnctoresistor in accordance with the amount said key means ismoved.

2. An electronic musical system as claimed in claim 1 wherein said firstresistance means is said magnetoresistor and said second resistancemeans is a fixed resistor.

3. An electronic musical system as claimed in claim 1 wherein said firstresistance means is a fixed resistor and said second resistance meansis'said magnetoresistor. v

4. An electronic musical system as claimed in claim 1 wherein both saidfirst and second resistance means are magnetoresistorsthe electricalresistance of which varies in accordance with the intensity of magneticfield applied thereto, and said magnet element is positioned close toand controls both of said magnetoresistors so that the electricalresistance of said magnetoresistors varies oppositely from each other.

5. An electronic musical system as claimed in claim 1 wherein saidmagnet element is a magnet having two opposite poles spaced from eachother, and said magnetoresistor faces one of said poles when said keymeans is not moved so as to be depressed and faces the other of saidpoles when said key means is depressed.

6. An electronic musical system as claimed in claim 5 wherein said twopoles are positioned in parallel in a horizontal direction.

7. An electronic musical system as claimed in claim 5 wherein said twopoles are arranged on a collinear vertical line.

1. An electronic musical system comprising a tone generator, a tonecoloring circuit, a first resistance means connected in a series circuitbetween said tone generator and said tone coloring circuit, a secondresistance means having one end connected to the series circuit betweensaid first resistance means and said tone coloring circuit and the otherend connected to ground, at least one of said resistance means being amagnetoresistor the electrical resistance of which varies in accordancewith the intEnsity of the magnetic field applied thereto, a key meansmovably supported in said system so as to be depressed when it is moved,and a magnet element mounted on said key means close to saidmagnetoresistor and controlling the electrical resistance of saidmagnetoresistor in accordance with the amount said key means is moved.2. An electronic musical system as claimed in claim 1 wherein said firstresistance means is said magnetoresistor and said second resistancemeans is a fixed resistor.
 3. An electronic musical system as claimed inclaim 1 wherein said first resistance means is a fixed resistor and saidsecond resistance means is said magnetoresistor.
 4. An electronicmusical system as claimed in claim 1 wherein both said first and secondresistance means are magnetoresistors the electrical resistance of whichvaries in accordance with the intensity of magnetic field appliedthereto, and said magnet element is positioned close to and controlsboth of said magnetoresistors so that the electrical resistance of saidmagnetoresistors varies oppositely from each other.
 5. An electronicmusical system as claimed in claim 1 wherein said magnet element is amagnet having two opposite poles spaced from each other, and saidmagnetoresistor faces one of said poles when said key means is not movedso as to be depressed and faces the other of said poles when said keymeans is depressed.
 6. An electronic musical system as claimed in claim5 wherein said two poles are positioned in parallel in a horizontaldirection.
 7. An electronic musical system as claimed in claim 5 whereinsaid two poles are arranged on a collinear vertical line.